JP5167657B2 - Brushless DC motor drive device and ventilation blower equipped with the drive device - Google Patents

Description

  The present invention relates to a drive device for a brushless DC motor used in a ventilation fan, for example, a ceiling-embedded ventilation fan embedded in a ceiling, and is supplied to an inverter circuit by using rectangular wave energization without using a position sensor. In a brushless DC motor drive device that detects the current waveform detected to estimate the rotor position and controls the energization phase by sensorless control, if the motor current value becomes small and cannot be detected due to low speed rotation or the like, the stator winding The present invention relates to a drive device that detects an induced voltage generated on a line and estimates and drives the position of a rotor, and detects and safely stops the state even when a brushless DC motor steps out and becomes abnormal.

  Conventionally, this type of brushless DC motor and its driving device are efficient (power saving) and superior in durability, so that it is used in a ventilation fan that is driven for a long time, such as a range hood or a ceiling-mounted ventilation fan. It is installed. Further, due to the demand for downsizing and cost reduction of the ventilation fan, downsizing and cost reduction of the brushless DC motor and its driving device are required. Furthermore, in order to improve comfort, stable ventilation with a small airflow for a long time and ventilation with a large airflow for a short time, and when a brushless DC motor steps out and stops, it reliably detects stepping out. It is required to stop safely.

  FIG. 5 shows an example in which a brushless DC motor and its driving device are mounted on a conventional ceiling-embedded ventilation fan and are actually installed on the ceiling. FIG. 5A is an explanatory view of a ceiling-embedded ventilation fan. A ceiling-mounted ventilation fan 118 has a brushless DC motor 102 and a brushless DC driving device 112 attached to a casing 115 and a blower fan 116 attached to a rotor 104. The ceiling-embedded ventilation fan is attached to the ceiling, and the brushless DC motor 102 is driven by the driving device 112 to ventilate the room to the outside. FIG. 5B shows the installation state of the ceiling-embedded ventilation fan. The ceiling-embedded ventilation fan 118 is embedded in the ceiling 120, and the indoor air is ventilated by exhausting it through the duct 119 to the outside of the room separated by the outer wall 121. I do.

FIGS. 6, 7 and 8 show a stator winding for an induced voltage induced in a stator winding of a brushless DC motor by detecting an induced voltage generated in the stator coil by detecting the position of the conventional rotor. to estimate the position of the rotor from the phase of the motor voltage to be applied, that has been known to control the energization so as to follow the target phase (for example, see Patent Document 1). There is also known a brushless DC motor driving device that detects and stops an abnormally excessive motor current value due to a step-out of the brushless DC motor. The operation of the brushless DC motor driving device will be described below.

  As shown in FIG. 6, the DC power source 105 supplies a DC voltage to the inverter circuit 101. The inverter circuit 101 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W-phase upper arm switching elements, respectively. Similarly, Q4, Q5, and Q6 are U, V, and W-phase switching elements, respectively. It is a lower arm switching element. Each switching element is connected in parallel with free-wheeling diodes D1, D2, D3, D4, D5, and D6. The brushless DC motor 102 includes a stator 103 and a rotor 104, and three-phase stator windings LU, LV, and LW are arranged on the stator 103 so as to have a phase difference of 120 degrees in electrical angle. In addition, PU, PV, and PW, which are induced voltage detection means 114, are connected to the stator winding, and output a position detection signal that estimates the position of the rotor as compared with the half voltage 113 of the DC power source 105. And output to the rotor position detecting means 118 incorporated in the microcomputer 110 of the brushless DC motor driving device 112. From the position detection signal, the rotor position estimating means 118 uses the pre-stored induced voltage induced in the stator windings LU, LV, LW and the phase of the motor voltage applied to the stator windings LU, LV, LW. The position of the rotor is estimated from the relationship and output to the energizing means 108. An example of the electronic component of the induced voltage detection means 114 is a comparator. The energization means 108 determines an energization signal so as to follow the target phase from the input position detection signal, and outputs it to the abnormality detection means 109.

  A current detection resistor 106 is disposed between the DC power supply 105 and the switching element as shown in the figure. The current detection means 107 built in the microcomputer 110 converts the voltage of the motor current value output from the current detection resistor 106 into a digital value by an A / D converter, and recognizes the motor current value. The abnormality detection unit 109 compares the motor current value output from the current detection unit 107 with a predetermined threshold value, and outputs an energization signal output from the energization unit 108 to the drive circuit 111 when the motor current value is small. To do.

  The drive circuit 111 applies the motor voltages U +, U−, V +, V−, W +, W− based on the energization signal output from the energization means 108 to the switching elements Q1, Q2, Q3, Q4, Q5, Q6 of the inverter circuit 101. Output to. The inverter circuit 101 actually drives the brushless DC motor 102 based on the energization signal of the drive circuit 111.

  Further, the abnormality detection means 109 compares the motor current value output from the current detection means 107 with a predetermined threshold value. If the motor current value is large, the abnormality detection means 109 is regarded as abnormal regardless of the energization signal from the energization means 108. A signal to be stopped is output to the drive circuit 111.

  The drive circuit 111 stops the energization signal of the motor voltage and outputs it to the switching elements Q1, Q2, Q3, Q4, Q5, Q6 of the inverter circuit 101. The inverter circuit 101 actually stops the brushless DC motor 102.

  FIG. 7 shows the waveforms of each part, and FIG. 7A shows PU, PV, PW input signals of the induced voltage detection means 114, and the motor voltage applied to the stator winding and the half voltage 113 of the DC power source 105. Input the waveform. The motor voltage has a so-called PWM waveform. FIG. 7B shows an output signal of the position detection signal. When the voltage is larger than the half voltage 113, H is output as the position detection signal. The rotor position detecting means 118 is stator-turned from the time TA until the induced voltage gradually increases to become an H signal after energization and the time TB until the induced signal gradually decreases and the L signal continues. The rotor position is estimated from the induced voltage induced on the wire and the phase of the motor voltage applied to the stator winding. If the target time is TM = 1 msec and TA = TB = 0.3 msec, the phase is detected from equation (1).

TA / TM = TB / TM = 0.3 / 1 = 0.3 (1)
And the phase is specified as -20 degrees.

  FIG. 7C shows the phase relationship between the induced voltage induced in the stator winding from TA and TB actually stored in advance by the rotor position estimating means and the motor voltage applied to the stator winding. It is a table | surface which shows.

  FIG. 8 shows an output waveform of the drive circuit 111, which outputs a combination of signals of motor voltages U +, U−, V +, V−, W +, W−. When the target phase is 0 degree, the control is always performed so that TA / TM = TB / TM = 1.

  FIG. 9A of FIG. 9 shows the motor current value detected by the current detection means 107. Since it actually becomes a PWM waveform, the A / D converter detects the motor current value during the period in which the current flows. In FIG. 9B, when the motor current value detected by the current detection means 107 becomes higher than the predetermined threshold value of the abnormality detection means 109, the output of the drive circuit 111 stops and the motor current flows. The missing waveform is shown.

  Here, due to the demand for downsizing and cost reduction of the ventilation fan, downsizing and cost reduction of the brushless DC motor and its drive circuit are required. Since the conventional brushless DC motor driving device can be driven without a sensor, a motor for position detection and a circuit board for mounting the sensor on the motor are not necessary, which has been helpful in reducing the size and cost of the brushless DC motor. However, the induced voltage detection means requires three comparators, and the driving device of the brushless DC motor becomes large and the cost is high. Therefore, further downsizing and cost reduction are required. Therefore, the present applicant has invented a sensorless drive circuit for a brushless DC motor that detects and rotates a motor current by energizing a rectangular wave.

  Based on the motor current value supplied from the DC power supply to the inverter circuit, the rotor position is estimated from the phase of the induced voltage induced in the stator winding of the brushless DC motor and the motor voltage applied to the stator winding. The energization is controlled so as to follow the target phase. By eliminating the induced voltage detection means PU, PV, and PW, the cost and size of the brushless DC motor and its driving device can be reduced.

  The operation of Japanese Patent Application No. 2005-275732 will be described below with reference to FIGS. As shown in FIG. 10, a current detection resistor 106 for detecting a motor current value supplied from the DC power source 105 to the inverter circuit 101 is arranged. The voltage of the current detection resistor 106 is input to the current detection means 107 built in the microcomputer 110. The current detection means 107 is an A / D converter. The rotor position estimating means 118 calculates the current change rate with the passage of time from the motor current value digitized by the current detecting means 107 and compares it with the current change rate stored in advance to estimate the rotor position. .

  The abnormality detection unit 109 compares the motor current value output from the current detection unit 107 with a predetermined threshold value, and outputs an energization signal output from the energization unit 108 to the drive circuit 111 when the motor current value is small. To do. The drive circuit 111 outputs the motor voltage signals U +, U−, V +, V−, W +, W− based on the energization signal output from the energizing means 108 to the switching elements Q1, Q2, Q3, Q4, Q5 of the inverter circuit 101. Output to Q6. The inverter circuit 101 actually drives the brushless DC motor 102 based on the energization signal of the drive circuit 111.

  Further, the abnormality detection means 109 compares the motor current value output from the current detection means 107 with a predetermined threshold value, and when the motor current value is large, the abnormality detection means 109 stops as an abnormality regardless of the signal from the energization means 108. The signal to be output is output to the drive circuit 111. Since other parts are the same as those of the conventional brushless DC motor driving apparatus, description thereof is omitted.

  FIG. 11 shows the waveform of each part, and FIG. 11A is an explanatory diagram in which the current detection means 107 detects the motor current value from the current waveform. FIG. 11B shows the stator windings LU, LV, LW with respect to the current change rate of the motor current value stored in advance by the rotor position estimating means and the induced voltages induced in the stator windings LU, LV, LW. It is a table | surface which shows the phase relationship with the motor voltage applied to.

  For example, when I1 = 0.5A and I2 = 0.6A, the current change rate is expressed by equation (2).

Current change rate = I2 / I1 = 0.6 / 0.5 = 1.2 (2 )
And the phase is estimated to be -20 degrees. FIG. 11C shows an example of a current waveform when the current change rate actually changes. Since the current change rate changes when the phase deviates from 0 degrees, the energization is always controlled so that the same current change rate is obtained. For example, if the target phase is 0 degree, the control is always performed so that I2 / I1 = 1.24. When the phase shifts, the motor current value increases. This is because the magnitude of the induced voltage of the rotor 104 becomes small.

  By adopting such a configuration, the induced voltage detection means is not necessary, and the motor current value output from the current detection resistor 106 can be detected and driven, so that the brushless DC motor driving device can be reduced in size and reduced in size. And lower costs.

JP-A-6-253588

However, in such a conventional configuration, in order to improve comfort in recent years, it is required to stably ventilate for a long time with a slight air volume. Since it is minimized, there is a problem that the motor current value of the current detection means 107 cannot be detected and the phase that is the position of the rotor cannot be estimated. In addition, when the ceiling-embedded ventilation fan is ventilating, if air flows from the room to the outside due to the outdoor wind and external force is applied to the blower fan 116, the motor current of the brushless DC motor disappears, and the current detection means 107 becomes Since the current value cannot be detected , there is a problem that the phase that is the position of the rotor cannot be estimated.

  FIG. 12 shows the state of the motor current when an external force is applied to the blower fan 116 of the ceiling-embedded ventilation fan. FIG. 12A shows a state in which the blower fan 116 receives an external force due to the wind outside the ceiling embedded ventilation fan. The ceiling-mounted ventilation fan 118 exhausts the indoor air through the duct 119 as indicated by an arrow and applies an external force to the blower fan 116. (Refer to FIG. 5 for the blower fan 116) FIG. 12B shows an example of the current detected by the current detection means 107 when air flows from the room to the room and an external force is applied to the blower fan 116.

  Therefore, it is conceivable that an amplifier 122 that amplifies the current waveform is connected to the current detection means 107 to amplify the reduced current and detect the current waveform. (C) shows an example in which an amplifier 122 is connected to the current detection means. Since the current waveform of the amplifier changes at a high speed, it is necessary to use an expensive high-speed amplifier, which increases the cost and there is a problem that the cost cannot be reduced. An example of the amplifier is a high-speed operational amplifier.

  Similarly, when a brushless DC motor steps out due to locking or sensorless driving, it is required to detect step-out reliably and stop safely. Since the current becomes maximum, the motor current value of the current detection means 107 becomes maximum, there is no large difference from the predetermined threshold value of the abnormality detection means 109, the abnormality detection works, and it must be restarted was there. In addition, when the ceiling-embedded ventilation fan is ventilating, when air flows from the outside into the room due to the outdoor wind and an external force is applied to the blower fan 116, the motor current of the brushless DC motor increases, and the current detecting means 107 There is a problem that the motor current value further increases, exceeds a predetermined threshold value of the abnormality detection means 109, and abnormality detection does not work normally.

  FIG. 13 shows the state of the motor current when an external force is similarly applied to the blower fan 116 of the ceiling-embedded ventilation fan. FIG. 13A shows a state in which the blower fan 116 receives an external force by the wind outside the ceiling-mounted ventilation fan. The ceiling-mounted ventilation fan 118 is blown into the room through the duct 119 as indicated by an arrow, and applies an external force to the blower fan 116. (Refer to FIG. 5 for the blower fan 116) FIG. 13B is predetermined as a current detected by the current detection means 107 when air flows into the room from the outside and an external force is applied to the blower fan 116 to increase the motor current. An example of a given threshold is shown.

An object of the present invention is to provide a brushless DC motor driving apparatus capable of estimating the phase that is the position of the rotor even when the motor current value is minimized. Since it can be ventilated stably for a long time with the amount, and the induced voltage detection means is detected in one phase, it can be reduced in size and cost, and it can be ventilated by driving for a long time. when the brushless DC motor is stopped by loss of synchronism, and to provide a reliable driving device for a brushless DC motor capable of detecting the loss of synchronism and ventilation blower equipped with it.

In order to achieve the above object, a brushless DC motor driving apparatus according to the present invention has a three-phase stator winding and a rotor connected via an inverter circuit in which a plurality of switching elements are bridge-connected to a DC power supply. A brushless DC motor driving apparatus for rotating a brushless DC motor having a switching element of the inverter circuit on and off, a current detection resistor for detecting a motor current value supplied from the DC power source to the inverter circuit, and a motor current Current detection means for detecting the current waveform from the value, induced voltage detection means for detecting the induced voltage generated in the stator winding, rotor position estimation means for estimating the position of the rotor from the current waveform and the induced voltage, to determine the actual position of the rotor from the position of the rotor according to the estimated current waveform and an induced voltage from the rotor position estimation unit A position detection determination means, a drive device for a brushless DC motor example Bei energization means for energizing based on the position of the rotor, said position detecting determining means provided a predetermined threshold to the motor current value When the motor current value is smaller than the threshold value, the rotor position is detected by the induced voltage detection means, and when the motor current value is larger than the threshold value, the rotor position is detected by the current detection means. It is characterized by this.

By this means, the rotor position is estimated from the current waveform when the motor current value is large with respect to a predetermined threshold value for the motor current value, and by the induced voltage when the motor current value is small. By estimating the rotor position, it is possible to obtain a brushless DC motor driving apparatus that can detect the rotor position even if the motor current value becomes minimum and the current waveform cannot be detected .

  The other means is that the induced voltage detection means detects the induced voltage of any one of the three-phase stator windings, and determines the actual rotor position from the current waveform and the rotor position based on the induced voltage. Is to be judged.

  By this means, the induced voltage detection means can be realized by any one-phase induced voltage detection circuit, and a drive device for a brushless DC motor that can be reduced in size at low cost can be obtained.

  Another means is that the abnormality detection means stops the brushless DC motor when the position of the rotor estimated by the current detection means and the induced voltage detection means is greater than a predetermined value. It is.

  By this means, when the brushless DC motor steps out and stops, there is a difference in the estimation of the rotor position. Therefore, a brushless DC motor drive device that can reliably detect the step out and stop safely is obtained. It is done.

Further, another means is a ventilation blower equipped with the brushless DC motor driving device according to any one of claims 1 to 3 .

  By this means, it is possible to obtain a ventilating air blower that can stably ventilate for a long time with a slight air volume, or can reliably detect the step-out and stop safely when the brushless DC motor steps out and stops.

  According to the present invention, since the phase can be estimated even when the motor current value is minimized, it is possible to ventilate stably for a long time with a small air volume, or to detect the induced voltage detecting means in one phase, thereby reducing the size. The brushless DC motor drive device that can reduce the cost and can detect the step-out reliably when the brushless DC motor steps out and stops because it is driven and ventilated for a long time. And a ventilation blower equipped with it can be provided.

The figure which shows the drive device of the brushless DC motor of Example 1 of this invention. The figure which shows the waveform of each part of the drive device of a brushless DC motor ((a) The figure which shows the input waveform of the induced voltage detection means, (b) The figure which shows the output waveform of the induced voltage detection means and the current detection means, (C) A diagram showing the output waveforms of the actual induced voltage detection means and current detection means and the determination of the position detection determination means) The figure which shows the waveform of each part when a brushless DC motor steps out (a) The figure which shows the input waveform of the induction voltage detection means, (b) The induction voltage detection means Actual induction voltage detection means and current detection Figure showing the output waveform of the means and the judgment of the position detection judgment means) The figure which shows the ceiling embedded type ventilation fan which mounts the drive device of the brushless DC motor of this invention ((a) same front view, (b) same side view, (c) same top view) The figure which shows the conventional ceiling embedded type ventilation fan ((a) same front view, (b) same side view, (c) the same plan view, (d) The example where the ceiling embedded type ventilation fan was actually installed in the ceiling Figure showing The figure which shows the drive device of the brushless DC motor which detects a rotor position from an induced voltage similarly The figure which shows the waveform of each part of the drive device of a brushless DC motor similarly The figure which shows the output waveform of the drive circuit of the drive device of a brushless DC motor similarly The figure which shows the waveform of the drive device of a brushless DC motor ((a) The figure which shows the waveform which the current detection means of the drive device detects, (b) The abnormality detection means of the drive device detects abnormality, and the drive means (Figure showing the waveform when stopping) The figure which shows the drive device of the brushless DC motor which detects a rotor position from a motor electric current value similarly The figure which shows the waveform of each part of the drive device of a brushless DC motor ((a) The explanatory view in which a current detection means detects a motor current value, (b) The figure which estimates a phase, (c) Current change rate is actually Figure showing current waveform when changed) Explanatory drawing when external force is applied to the ceiling embedded ventilation fan from the room to the outside ((a) A diagram showing how the blower fan 116 receives external force, (b) Current detection when the blower fan is applied with external force Current waveform diagram detected by means, (c) A diagram showing an example in which an amplifier is connected to the current detection means) Explanatory drawing when external force is applied to the ceiling-embedded ventilation fan from the outside to the inside of the room ((a) A diagram showing how the blower fan 116 receives external force, (b) Current detection when the external force is applied to the blower fan Current waveform diagram detected by means)

According to a first aspect of the present invention, there is provided a brushless DC motor having a three-phase stator winding and a rotor connected via an inverter circuit formed by bridge-connecting a plurality of switching elements to a DC power source. In a brushless DC motor driving apparatus that rotates by turning on and off a switching element of a circuit, a current detection resistor that detects a motor current value supplied to the inverter circuit from the DC power supply, and a current that detects a current waveform from the motor current value Estimated by a detecting means, an induced voltage detecting means for detecting an induced voltage generated in the stator winding, a rotor position estimating means for estimating a rotor position from the current waveform and the induced voltage, and the rotor position estimating means Position detecting / determining means for determining the actual rotor position from the rotor position based on the generated current waveform and the induced voltage, and based on the rotor position. A drive device for a brushless DC motor example Bei energization means for energizing you are, the position detecting determining means provided a predetermined threshold with respect to the motor current value when the motor current value is smaller than the threshold Is a brushless DC motor drive device that detects the rotor position from the induced voltage detection means and detects the rotor position from the current detection means when the motor current value is larger than the threshold value. is there.

  As a result, the position can be estimated from the induced voltage even if the motor current value becomes minimum and the current waveform cannot be detected.

The invention according to claim 2 of the present invention, apparatus for driving a brushless DC motor according to claim 1, induced voltage detecting means detects at any one phase of the induced voltage of the three-phase stator windings This is a brushless DC motor driving apparatus that determines the actual rotor position from the rotor position based on the current waveform and the induced voltage.

  As a result, the brushless DC motor drive device can be reduced in size at low cost.

According to a third aspect of the present invention, in the brushless DC motor drive device according to any one of the first to second aspects, the abnormality detecting means has a rotor position estimated from the current detecting means and the induced voltage detecting means. The brushless DC motor driving apparatus is configured to stop the brushless DC motor when there is a difference equal to or greater than a predetermined value.

  As a result, the drive unit of the brushless DC motor can reliably detect the stop and stop safely.

A fourth aspect of the present invention is a ventilation air blower equipped with the brushless DC motor control device according to any one of the first to third aspects.

  As a result, when the ventilation fan blows stably for a long time with a slight air flow to improve comfort, or when the brushless DC motor steps out and stops, it will reliably detect step out and stop safely can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, a current detection resistor 6 for detecting a motor current value supplied from the DC power supply 5 to the inverter circuit 1 is arranged. The voltage of the current detection resistor 6 is input to the current detection means 7 built in the microcomputer 15. The current detection means 7 is an A / D converter. The rotor position estimating means 8 calculates a current change rate with respect to time of the current value from the motor current value digitized by the current detecting means 7 and is induced in the stator windings LU, LV, LW stored in advance. The current change rate determined from the phase relationship of the motor voltage applied to the stator windings LU, LV, and LW with respect to the induced voltage is compared, and the phase that is the position of the rotor is estimated.

  On the other hand, an induced voltage detecting means 12 is connected to the stator winding, and compared with the half voltage 13 of the DC power source 5 and outputted to the rotor position estimating means 8. An example of an electronic component of the induced voltage detection means 12 is a comparator. The rotor position estimating means 8 estimates the phase of the motor voltage applied to the stator winding 3 with respect to the induced voltage induced in the LU of the stator winding 3 from the input signal. The position detection determination means 9 is determined in advance as the motor current value output from the current detection means 7 for the two phases estimated by the current detection means and the induced voltage detection means output from the rotor position estimation means 8. When the motor current value is larger than the threshold value, the phase estimated from the current detection means 7 is adopted. On the contrary, when the motor current value is small, the phase estimated from the induced voltage detection means 12 is adopted. Output. The energization means 10 is controlled so as to always have the same phase from the input position detection signal.

  The abnormality detection unit 11 compares the motor current value output from the current detection unit 7 with a predetermined current value. If the motor current value is smaller, the abnormality detection unit 11 sends an energization signal output from the energization unit 10 to the drive circuit 14. Output. The drive circuit 14 outputs the motor voltage signals U +, U−, V +, V−, W +, W− based on the energization signal output from the energization means 10 to the switching elements Q1, Q2, Q3, Q4, Q5 of the inverter circuit 1. Output to Q6. The inverter circuit 1 actually drives the brushless DC motor 2 based on the motor voltage signal of the drive circuit 14.

  Further, the abnormality detection means 11 compares the motor current value output from the current detection means 107 with a predetermined current value. When the motor current value is large, the abnormality detection means 11 stops as an abnormality regardless of the signal from the energization means 10. The signal is output to the drive circuit 14.

  FIG. 2 shows the waveform of each part, and FIG. 2A shows the input waveform of the induced voltage detection means 12 and the waveform of the one-phase stator winding LU. FIG. 2B shows output waveforms of the induced voltage detection means 12 and the current detection means 7. The induced voltage detection means 12 has H and L waveforms, and the current detection means 7 has a digital value. FIG. 2C shows an example of the output waveforms of the actual induced voltage detection means 12 and the current detection means 7 and the determination of the position detection determination means 9. When larger than a predetermined threshold value of the motor current value, for example, when 0.3A is set as a threshold value and larger than 0.3A, the estimated phases from No. energization to No are indicated. The phase estimated by the induced voltage detection means 12 and the current detection means 7 is performed for each energization. However, when the threshold value is smaller than 0.3 A, the motor current value is extremely small and cannot be detected, so the value is not calculated. In the table, “No” to “No” are not calculated. Since the phase estimated by the induced voltage detection means 12 can be estimated only at the timing when TA or TB is measured, the previous value is adopted when it cannot be estimated. For example, the phase estimated with No in the table is the same value for No and Ha. Since the motor current value is smaller than 0.3 A from No. C, the value of the induced voltage detection means 12 is adopted. Although the motor current value has increased from No., since the estimated phase uses No, the phase is delayed and the motor current value further increases. In No, the motor current value becomes larger than the threshold value, the phase is estimated by the current detection means 7, and the phase is estimated every time, so that the target phase is quickly obtained. If the phase shifts, the induced voltage becomes small and the motor current value becomes large. On the contrary, the induced voltage detecting means 12 is switched to the current detecting means 7, and it can be understood that the phase can be stably followed.

  As a result, even if the motor current value becomes a minimum and the current waveform cannot be detected, the phase can be estimated by the induced voltage, so that the driving can be stably performed even at a low rotation, and the induced voltage detecting means is a one-phase induced voltage. Since it can be realized by the detection circuit, a brushless DC motor drive device that can be reduced in size at low cost can be obtained.

  In this embodiment, a specific example of the threshold value of the motor current value is shown. However, this numerical value may be determined in accordance with the characteristics of the motor and the accuracy of the current detection means, and there is a difference in the operational effect. Does not occur.

(Embodiment 2)
The abnormality detection means 11 obtains the phase difference estimated by the rotor position estimation means 8 from the current detection means 7 and the induced voltage detection means 12 and compares it with a predetermined phase difference. Is output to the drive circuit 14 to actually drive the brushless DC motor 2. On the other hand, if it is large, a signal to be stopped as an abnormality is output to the drive circuit 14 regardless of the signal from the energizing means 10, and the brushless DC motor 2 is actually stopped.

  FIG. 3 shows waveforms at various parts when the brushless DC motor 2 has stepped out. FIG. 3A shows an input waveform of the induced voltage detection means 12. Since the brushless DC motor 2 is stopped, an induced voltage is not generated, and a waveform as shown in the figure is obtained. FIG. 3B is an explanatory diagram in which the output waveforms of the actual induced voltage detection means 12 and the current detection means 7 and the abnormality detection means 11 detect the phase difference and stop. In the induced voltage detection means 12, since the brushless DC motor 2 is stopped but the drive circuit 14 is operating, the rotor 4 repeats a slight vibration every time it is energized. The operation repeats the 30 degree phase alternately. On the other hand, since no induced voltage is generated in the current detection means 7, the voltage changes according to the inductance of the stator winding of the brushless DC motor 2, and has a waveform as shown in the figure as an example. In this case, the phase estimated by the current detection means 7 is −30 degrees. Since the motor current value is only the resistance of the stator winding, it becomes a large motor current value, and the predetermined threshold value of the position detection determination means 9 is always exceeded.

The rotor position estimating means 8 detects the phase difference from the equation (3), assuming that the phase estimated by the induced voltage detecting means 12 is φY and the phase detected by the current detecting means 7 is φD.

Phase difference = φY-φD ·· · (3 )
If the predetermined threshold value is, for example, ± 40 degrees, for example, in the case of No, the phase difference becomes 0 degrees and does not become abnormal. On the other hand, for example, in the case of No, the phase difference is 60 degrees, and it is determined that an abnormality has been detected, and the brushless DC motor 2 is stopped.

  As a result, when the brushless DC motor steps out and stops, there is a difference in the estimation of the rotor position, so that a brushless DC motor drive device that can reliably detect the step out and stop safely can be obtained. .

  In the present embodiment, a specific example of the threshold value of the phase difference is shown. However, this numerical value may be determined in accordance with the characteristics of the motor, and there is no difference in the operational effect.

(Embodiment 3)
FIG. 4 shows a conventional ceiling-mounted ventilation fan in which the brushless DC motor driving device of the present invention is mounted.

  As a result, when the ventilation fan blows stably for a long time with a slight air flow to improve comfort, or when the brushless DC motor steps out and stops, it reliably detects overcurrent and stops safely be able to.

DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Brushless DC motor 3 Stator winding 4 Rotor 5 DC power supply 6 Current detection resistance 7 Current detection means 8 Rotor position estimation means 9 Position detection judgment means 10 Current supply means 11 Abnormality detection means 12 Induced voltage detection means 13 1/2 voltage 14 drive circuit 15 microcomputer 16 drive device

Claims (4)

A brushless DC motor having a three-phase stator winding and a rotor connected via an inverter circuit in which a plurality of switching elements are bridge-connected to a DC power supply is rotated by turning on and off the switching elements of the inverter circuit. In the brushless DC motor driving apparatus, a current detection resistor for detecting a motor current value supplied from the DC power source to the inverter circuit, a current detection means for detecting a current waveform from the motor current value, and a stator winding An induced voltage detecting means for detecting an induced voltage; a rotor position estimating means for estimating a rotor position from the current waveform and the induced voltage; a current waveform estimated by the rotor position estimating means; a position detection determining means for determining the actual position of the rotor from the position and example Bei energization means for energizing based on the position of the rotor A drive unit for a lashless DC motor, wherein the position detection determination means provides a predetermined threshold value for the motor current value, and when the motor current value is smaller than the threshold value, the position detection determination means rotates by the induced voltage detection means. A brushless DC motor drive device characterized by detecting the position of a child and detecting the position of the rotor from current detection means when the motor current value is larger than the threshold value . The induced voltage detecting means detects an induced voltage of any one of the three-phase stator windings, and judges an actual rotor position from a current waveform and a rotor position based on the induced voltage. The brushless DC motor drive device according to claim 1 . The abnormality detection means detects an abnormality when the position of the rotor estimated by the current detection means and the induced voltage detection means is greater than a predetermined value, and the energization means energizes the inverter circuit based on the abnormality detection. 3. The brushless DC motor driving device according to claim 1, wherein the driving device is stopped. A ventilation blower equipped with the brushless DC motor driving device according to any one of claims 1 to 3 .

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